1. Field of the Invention
The present invention relates to an ignition device for an internal combustion engine for driving spark plugs arranged to each cylinder of the internal combustion engine.
2. Description of the Related Art
Generally, a conventional ignition device for an internal combustion engine is constructed with a plurality of spark plugs arranged to each cylinder. When an ignition device for an internal combustion engine is constructed as mentioned above and a plurality of spark plugs are used and are simultaneously ignited at a single cylinder, effects obtained are good combustion inside the cylinder, improvement of fuel efficiency, improved gas mileage, enabling of lean combustion, and the like (see, for example, Japanese Patent Laid-Open Publication No. Hei 1-232165, pp. 5-7, FIG. 3).
However, the ignition device for an internal combustion engine described above has the following problems. Namely, each spark plug is independently provided with an ignition coil, an electrical supply circuit for controlling the electrical supply to the ignition coil, and the like. Therefore, it is difficult to avoid an ignition device that increases in size and costs. Therefore, in a case where two spark plugs are arranged per cylinder, for example, the number of ignition coils and the number of electrical supply circuits will double compared to a construction where one ignition plug is furnished to one cylinder.